Alcoholic Liver Disease (ALD) remains a major cause of alcohol-related morbidity and mortality. 15-30% of heavy drinkers develop advanced ALD, over 25,000 deaths occur annually related to liver disease, and over 40% of those are attributed to alcoholic cirrhosis. Major advances have been made in our understanding of mechanisms of ALD, especially related to oxidative stress, cytokines, mitochondrial dysfunction and adduct formation. However, there is no FDA-approved therapy for alcoholic hepatitis or cirrhosis, and our understanding concerning disease pathogenesis remains incomplete. The emergence of the obesity epidemic (non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) as the hepatic manifestations of the metabolic syndrome) has provided new insights into mechanisms of liver injury. The "two-hit" theory for NASH that a baseline of fatty liver plus one of multiple second "hits" initiates the progression from steatosis to more serious liver injury, steatohepatitis. Similarly, most patients who drink heavily develop steatosis but only a few develop steatohepatitis, and similar mechanisms or "hits" for disease progression to alcoholic steatohepatitis (ASH) have been postulated. Lastly, we have recently reported that environmental toxicants (TASH) can produce steatohepatitis indistinguishable histologically from that produced by obesity or alcohol. We are in a unique situation to utilize a proteomics/ metabolomics approach for discovery of biomarkers for alcoholic liver disease and specifically alcoholic steatohepatitis. We have a one-of-a-kind database/repository in which we have a large number of serum/plasma specimens from well-characterized patients with severe alcoholic hepatitis, well-characterized NASH, and a highly-novel patient population of well-characterized TASH. Thus, we will be able to compare/ contrast the proteomics/metabolomics signatures in specimens from well-characterized patients with diverse steatohepatitis. We will also compare the results from the human ASH studies with experimental ASH samples from our ULARC rodent repository. Specific Aims of this proposal address the following 3 questions: 1) Are there biomarkers determined by proteomics/metabolomics that are common to ASH, NASH and TASH that indicate mechanistic commonalities in steatohepatitis?;2) Are there unique biomarkers for ASH compared with NASH/TASH?;and 3) Are there biomarkers for ASH that predict prognosis/outcomes? PUBLIC HEALTH RELEVANCE: The Research Area explored in this proposal is "Molecular Markers of Alcohol Exposure and Alcohol-Induced Tissue Injury". We postulate that there are metabolic pathways and biomarkers that can be defined by proteomics and metabolomics that are common to Alcoholic Steatohepatitis (ASH), Non-Alcoholic Steatohepatitis (NASH) and Toxicant Associated Steatohepatitis (TASH). Furthermore, we predict that ASH may have unique biomarkers/metabolic pathways, and differences may be seen in patients who resolve their disease compared to those who are having ongoing injury or die.